Conventional retractors are known in this field which have the form of spatulate hooks.
This type of retractor is also used in minimally invasive surgery.
In the case of intrathoracic surgery performed without a sternotomy, it is necessary to exert traction from the outside, either by an operating surgeon holding the retractor via a handle, or by fastening it to the surrounding tissues, which includes the rib cage, or by threads passing through the rib cage.
There are also retractors that can be described as peripheral retractors, which are used for example in eye surgery (see U.S. Pat. No. 6,083,155).
However, this type of retractor can be used only in operations in which there is no problem of access and in which the operating field is not deep. Pneumatic retractors formed by an inflatable cuff are also known from U.S. Pat. No. 5,342,385. This type of retractor, which is of considerable size, poses problems of deflation if torn by a cutting instrument.
Retractors specifically designed for spinal surgery are also known from US 2004/116954 and from WO 2004/021899. These retractors comprise, mounted at the end of a cylindrical tube, a truncated cone part in the shape of a funnel (widening toward the distal part). This is a relatively complex device which has to be deployed with force. Moreover, this type of retractor does not permit direct viewing of the operating field, and the<<keyhole>>view produced is advantageous only if the eye of the camera is near the incision, which is not always the case.